1. Field of the Invention
This invention relates to a centrifugal refining crusher in which ores and rocks are crushed and refined by throwing them out into housings surrounding respective rotors, making use of centrifugal force generated by the rotation of the rotors.
2. Description of the Prior Art
There were available the same kind of centrifugal crushers or refiners such as Japanese Utility model Publication No. 30599/1968 "Balls for Centrifugal Crusher", Japanese Patent Publication No. 33785/1978 "Lump Breaker" and Japanese laid-open Publication No. 216744/1986.
These crushers or refiners according to the prior art intended to crush or refine feed material such as ores and rocks by dropping the feed material essentially onto the center of the rotor rotating at a high speed and throwing out the material into the housing surrounding the rotor taking advantage of the centrifugal force.
However, because all crushers and refiners according to the prior art attempted to crush or refine material only by one-time throwing from the rotor, there was a certain level of limit to the crushing or refining effect, which results in a poor crushing ratio and a low shape factor (degree of roundness by solid content in aggregates).
And the limited crushing and refining effect has brought about another restriction on the size of feed material to be charged.
To solve the above problems, there came in an enhanced type of crushers and refiners such as Utility model Publication No. 8658/1964 "Vertical Impact Crusher", and such "Grain-Shape Refiner" as disclosed respectively in Patent laid-open Publications No. 197158/1987, No. 17159/1987 and No. 197160/1987.
The former "Vertical Impact Crusher" is designed to have two or more times crushing by vertically disposing a plurality of discs with striking plates (equivalent to aforesaid rotor) and a plurality of impact plates (equivalent to aforesaid housing). This repeated crushing can obtain a large crushing ratio, but it has little effect of refining, thus necessitating a further refining by another machine, resulting in a poor productivity.
The latter "Grain-Shape Refiner" intends to make two or more refining by vertically arrangeing two or more stages of combination of rotor and annular grinding chamber (equivalent to aforesaid housing). This repeated refining can improve the shape factor (degree of roundness by solid content in aggregates) representing the degree of roundness, but because the crusher is designed only for refining, feed material must previously be crushed and processed to an acceptable size using another crusher, thus resulting in a poor productivity similar to the former crusher.
And, in the prior art, the first rotor, the second rotor and the rotor boss connecting the both rotors are made inseparably into one piece. As a result, the diameters of both rotors are fixed, thus resulting in a failure to change the peripheral speed of the rotors corresponding to the size, nature, amount and usage of feed material and to change the ratio of the peripheral speeds of the both rotors.
In general, the crushers or refiners according to the prior art develop a large degree of local wear due to the abrasion by the feed material, thus requiring periodic repair or replacement, particularly in the two stage refiner in which excessive local wear is likely to occur because of different wear speeds necessitate the replacement of the total parts.
And again the two stage refiner produces a local heavy wear on the rotor boss due to the abrasion by the feed material flowing from the first housing into the second rotor, thus resulting in a high repair cost--the part can be repaired or strengthened by hard facing--and also eventually in a total replacement because several times of hard facing may cause thermal distortion of the part leading to a failure of rotation.
To protect the inside surface of the rotor from wearing, the "Rotor for Grain Shape Refiner" disclosed in the Patent laid-open Publication No. 241558/1987 is well known to have the lining protection.
The liners on the rotor consist of the bottom liner, side liner and top liner. Horizontal movement of the bottom liner is prevented by providing the bottom liner with the same shape (gradually narrowing outlet) as the bottom face of the outlet path, narrower in width at the outlet side. The horizontal movement of the side liner is prevented by the groove on the backside engaging with the projecting lug vertically provided on the rotor body and by the projecting lug at the lower end inserted in between the side face of the outlet path and the bottom liner. The vertical movement of the bottom liner and the side liner is prevented by the projecting lug at the top end of the side liner inserted in between the top liner attached to the top cover and the side face of the outlet path. Therefore, liner replacement requires the removal of the top cover, thus taking a lot of time and labor.